At present, the lithium-ion battery has been widely used in electronic products such as mobile phones, laptops and cameras. At present, the commercial lithium-ion battery mainly uses graphite as the negative active material, but its specific discharge capacity has been close to a theoretical value of graphite (372 mAh/g), therefore it is difficult to further increase the specific discharge capacity of the lithium-ion battery by processing a modification technology on the graphite. The theoretical value of the lithium metal is as high as 3860 mAh/g, and the electrode potential of the lithium metal is as low as −3.04V (vs. H2/H+), so the development of the lithium secondary battery using the lithium metal as the negative electrode has aroused the attention of researchers. However, there are two main obstacles in the further development of the lithium secondary battery: (1) the lithium dendrite is easily formed during cycle processes of the lithium secondary battery, the lithium secondary battery is easily short-circuited; (2) the lithium dendrite has a large surface area, a high reactivity and easily reacts with electrolyte, therefore the SEI membrane formed on the surface of the lithium metal is ceaselessly destroyed and formed, the electrolyte and the lithium ions are ceaselessly consumed, thereby decreasing cycle efficiency of the lithium secondary battery and shortening the cycle life of the lithium secondary battery. Therefore, how to effectively improve the surface properties of the lithium metal and inhibit the growth of the lithium dendrite is the key issue in the further development of the lithium secondary battery.
At present, many studies are focused on adding functional additive agents into the electrolyte, such as vinylene carbonate (VC), fluoroethylene carbonate (FEC), 2-methylfuran (2Me-F), alkali metal cations and the like. These functional additive agents can react with the lithium metal via adsorption reactions, decomposition reactions, polymerization reactions and the like to form a new protective membrane on the surface of the SEI membrane so as to enhance the properties of the SEI membrane on the surface of the lithium metal, thereby improving the cycle performance of the lithium secondary battery. However, there is a problem that the in-situ formed protective membrane has a weak mechanical strength and cannot completely cover the SEI membrane on the surface of the lithium metal, therefore it cannot completely prevent the SEI membrane from being severely and ceaselessly destroyed and formed during the lithium deposition/dissolution processes which is caused by change of the lithium metal topography. The growth of the lithium dendrite and the problems caused by the lithium dendrite are not solved substantially. Therefore, it is imperative to explore and develop an effective lithium metal protection technology to inhibit the growth of the lithium dendrite, improve the cycle performance, the coulomb efficiency and the safety performance of the lithium secondary battery.